This application relates to and incorporates by reference Japanese patent application 2001-264204, which was filed on Aug. 31, 2001.
The invention relates to a controlled compressor apparatus, which is applicable to an air conditioning system of a so-called idle-stop vehicle, in which the engine is stopped when the vehicle stops.
A compressor control apparatus is shown in Japanese patent publication No. 2000-229516, in which a compressor unit is selectively actuated by an engine or a motor unit to operate a refrigeration apparatus. In this compressor control apparatus, the compressor unit is driven through an electromagnetic clutch when the engine is running. When the engine is stopped, the electromagnetic clutch is disengaged and the compressor unit is driven by the motor unit, which is powered with a battery.
Since a large amount of electric power is required to actuate the compressor unit, the motor unit is preferably confined to minimum necessary operation. The compressor unit is a variable displacement compressor of swash plate type. Before the engine is stopped, the displacement of the compressor unit is increased to lower the cooling temperature. The displacement is then reduced, and the compressor unit is driven by both the engine and the motor unit. Subsequently, the electromagnetic clutch is disengaged and the engine is stopped so that the compressor unit is actuated by the motor unit alone This achieves a reduction in power consumption by driving the compressor unit by the motor unit.
The control to adjust the displacement of the compressor unit, however, is exercised based on the tilt angle of the swash plate. Detecting the tilt angle complicates the internal structure of the compressor unit and increases costs.
Variable displacement control, not only on swash plate type compressor units but in general, is often performed based on the cooling temperature and the internal pressure of the refrigeration circuit. This temperature and pressure are associated with the displacement only indirectly, and unnecessary power consumption of the motor unit occurs due to response delays.
In view of the foregoing problem, it is an object of the present invention to provide a controlled compressor apparatus that allows easy, precise variable control of displacement and reduces unnecessary power consumption under motor-driven operation.
To achieve the foregoing object, the invention according to a first aspect is a controlled compressor apparatus for use in a vehicle having an engine to be stopped when the vehicle comes to a temporary halt while moving. The apparatus includes: a compressor unit of variable displacement type for compressing a refrigerant, the compressor unit being included in a refrigeration apparatus; a motor unit powered by a battery; a control unit for selecting the engine or the motor unit to drive the compressor unit and for controlling the displacement of the compressor unit; and current detector for detecting a current value supplied to the motor unit. The control unit stores a correlation characteristic between the displacement and the current value in advance, and controls the displacement based on the current value detected by the current detector.
The displacement of the compressor unit is adjusted to be proportional to the load torque of the compressor unit, i.e., the driving torque of the motor unit. Since the driving torque is proportional to the current value of the motor, the displacement is proportional to the current value. The displacement can thus be controlled easily and almost directly with high precision, in terms of the current value. This eliminates unnecessary power consumption in actuating the compressor unit by the motor unit.
According to another aspect of the invention, the control unit minimizes the displacement of the compressor unit before it starts the motor unit to drive the compressor unit.
Consequently, the motor unit can be started at a minimum torque, which avoids excessive starting currents and reduces the starting power consumption. Since the starting current is not excessive, the motor unit can be simplified and reduced in size.
According to another aspect of the invention, the control unit increases the current value of the motor unit to a target current value corresponding to a required displacement while successively decreasing a current increasing rate so that the current value reaches the target current value without exceeding the target current value.
Consequently, without overshooting the target current value, the current value reaches the target current value in a short time, and the starting power consumption is reduced.
According to another aspect of the invention, the control unit increases the current value of the motor unit to a target current value corresponding to a required displacement so that the current value reaches the target current value through proportional-plus-integral-plus-derivative control.
Consequently, without a large overshoot, the target current value is reached in a short time and the starting power consumption is reduced.
According to another of the invention, the current detector is arranged near the battery.
This allows the displacement to be controlled in terms of the current value and allows the battery capacity to be checked as well, which prevents over-draining of the battery.
According to another aspect the invention, the control unit reduces the displacement of the compressor unit when the current value detected by the current detector exceeds a predetermined value.
The motor unit can thus be prevented from exceeding its maximum possible output torque, which prevents lockup of the motor.
According to another aspect of the invention, the control unit has an engine start request function for requesting an engine control unit, which controls operation of the engine, to start the engine, and the control unit stops the motor unit and exercises the engine start request function to start the engine when an integrated current value of the motor unit actuating the compressor unit exceeds a predetermined integral.
This prevents over-draining the battery. When the engine is started, the battery is charged for the next actuation of the motor unit.
In another aspect of the invention, the displacement of the compressor unit may be controlled in terms of a voltage value instead of the current value. This variation achieves the same effects achieved by the first aspect of the invention.
In another aspect of the invention, the compressor unit is suitably integrated with the motor unit and used as a hybrid compressor to be selectively powered by the engine or the motor unit.